Helm, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

271
FXUS66 KMFR 180545
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
945 PM PST Fri Jan 17 2025

.DISCUSSION...Updated Aviation Discussion...

&&

.AVIATION...18/06Z TAFS...Roseburg is reporting MVFR ceilings with
no restrictions of visibility as of 9:30 PM. However, a stratus
layer has been continuing to develop in the Umpqua Basin and in
Roseburg over the past hour that is expected to deepen near midnight.

A dry cold front will usher in a drier air mass, but low clouds and
fog have formed in the Umpqua Basin, Illinois and Rogue Valleys and
Grants Pass area tonight. The one thing the dry cold front could do
is shorten the duration of fog and low clouds.

Along the coast and just offshore. VFR conditions are expected
through the TAF period. VFR conditions are also expected east of the
Cascades through the TAF period. -Petrucelli/Hermansen

&&

.PREV DISCUSSION... /Issued 855 PM PST Fri Jan 17 2025/

DISCUSSION...GOES-West Nighttime Microphysics RGB shows fog
continuing to develop across the Rogue and Illinois Valleys this
evening. Visibility has bounced around at a quarter mile here at
the airport in the past hour as temperatures hover just above
freezing.

Developing offshore flow is indicated int the forecast soundings
with a much drier airmass set to descend on the terrain above
about 3000 feet, but the winds won`d be strong. We may see from
Talent to Ashland remain fog-free all night if winds channel in
and the airmass dries out.

Only the HRRR and NamNest indicate the lower visibilities in the
HREF ensemble, but the satellite tells a better story. Have gone
ahead and issued a freezing fog advisory tonight through noon
Saturday for zones 024-026 including Medford, Grants Pass, Cave
Junction.

The stratocumulus deck over the Umpqua was already in place from
late this afternoon but it continues to expand. Not confident in
them seeing widespread dense fog tonight as obs are showing good
visibility now with radiational cooling shut down. May be a brief
period of lower visibility there later tonight and early Saturday
morning.

East of the Cascades and in CA things generally look much drier
so clear and cold should remain the rule. Forecast beyond tonight
remain untouched. Stavish

PREV DISCUSSION... /Issued 300 PM PST Fri Jan 17 2025/

DISCUSSION...

A lot of the freezing fog has cleared out, although fog and some
stratus is lingering in a few of the valleys this afternoon as
high pressure remains in control. Some higher clouds are also
moving overhead filtering out the sun and keeping temperatures on
the cooler side this afternoon.

Heading into tonight it will be more of the same with MOS guidance
again hinting at some fog building into the valleys. Model
soundings shows some very dry air in the mid layers with lighter
east flow aloft. Given the persistent moisture trapped in the
valley, its hard to see freezing fog not forming again in the
Rogue, Illinois and Umpqua valleys with clear skies to the east
and south.

By Saturday afternoon, we are watching a coastal thermal trough
as temperatures stay warm around the Brookings area. Guidance is
suggesting highs in the mid 50`s, which should be the warmest
location in our forecast area on Saturday afternoon. Especially as
the fog could linger into the afternoon hours on Saturday given
how strong the inversion is.

By Sunday, the deep trough covering basically all the CONUS will
push a short wave down through Washington into Oregon. This will
help usher in some even cooler air and light east flow aloft. The
impacts on the public side will remain plenty of morning freezing
fog and cooler than normal temperatures across southern Oregon,
especially east of the Cascades into next week.

Otherwise, the best chance of rain is towards the end of next week
around Friday. The majority of ensemble members are bringing
precipitation to the Pacific Northwest towards the end of the
week with a 30 to 40 percent chance of rain or snow above 4000
feet. This doesn`t look like a real wet event looking at the
individual ensemble members, so just a lighter snow accumulation
in the mountains.

-Smith

MARINE...Updated 200 PM Friday, January 17, 2025...A thermal trough
remains along the south oregon coast resulting in moderate to
occasionally strong north winds into tonight. Winds will be strongest
south of Port Orford and beyond 10 nm from shore where the
combination of winds and seas will result in Hazardous Seas Warning
conditions.

The thermal trough will weaken late tonight into Saturday with north
winds gradually diminishing. Small Craft conditions are still likely
in the southern outer waters Saturday.

Winds and seas will continue to diminish Saturday night with winds
and seas remaining below advisory levels through at least the first
half of next week. -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Beach Hazards Statement from Saturday afternoon through Sunday
     afternoon for ORZ021-022.

     Freezing Fog Advisory from 1 AM to noon PST Saturday for ORZ024-
     026.

CA...None.

PACIFIC COASTAL WATERS...Beach Hazards Statement from Saturday
     afternoon through Sunday afternoon for PZZ350-356.

     Small Craft Advisory until 4 AM PST Saturday for PZZ350-356-370-
     376.

     Hazardous Seas Warning until 4 AM PST Saturday for PZZ356-376.

&&

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